Much of the power generation capacity in North America is provided by gas-fired turbines. These gas-fired turbines are general optimized to operate using fuel gas with a constant energy content, i.e. Wobbe Index. Significant variations in fuel gas energy content can result in the need for an extended shut down of the gas-fired turbine while the turbine control systems are adjusted to operate using the new fuel gas.
Where the fuel gas energy content variations do not require shut down of the gas-fired turbine, the change in fuel gas energy content results in substantial megawatt load swings, engine overfiring, and increased emissions of undesirable pollutants, such as NOX and CO. This is because the majority of gas turbine engines are designed using feedback control systems. Thus, while turbine component manufacturers design turbine components to handle the extreme firing temperatures and loads experienced during design conditions, turbine component life can be reduced due to extreme temperatures or forced caused by overfiring, megawatt load swings, or both.
Where gas-fired turbine control systems are designed to accommodate fuel gas energy content changes, the control systems generally use feedback loops that analyze the temperature of gases exiting the turbine or the level of pollutants exiting the turbine. The amount of energy supplied by the fuel gas is then adjusted by heating or cooling the fuel gas or injecting an inert into the fuel gas. However, by the time the adjustment is made, the gas turbine engine has already experienced a megawatt load swing, which can damage turbine engine components. These prior art systems also generally fail to address operational issues including, but not limited to, increased combustor dynamics, increased flashback potential and reduced start-up reliability. Thus, a need exists for an improved gas-fired turbine engine.